Device For Concentration Of Material On A Water Surface And Use Of The Device

ABSTRACT

A device for concentration of material on a water surface, wherein the device forms a front opening and is provided with buoyancy bodies and guide elements structured for guiding the material towards a collection portion, wherein the device is structured for admitting water through the device in the flow direction of the water, and wherein the device, in a portion thereof, is provided with at least two consecutive guide elements in the flow direction of the water.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority to Norwegian Patent Application No.20100144 filed 29 Jan. 2010 which is incorporated by reference herein.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not Applicable

REFERENCE TO A SEQUENCE LISTING SUBMITTED ON COMPACT DISC

Not Applicable

BACKGROUND OF THE INVENTION

The invention concerns a device for concentrating material located on ordirectly below a water surface. The material may comprise oil pollutionor some other type of pollution, floating waste or live or dead organicmaterial. The device is towed on the water surface, for example in theopen sea or on a lake or, alternatively, the water with the material mayflow through the device, for example by virtue of the device coveringthe surface of a portion of a river. More particularly, the inventionconcerns a device provided with at least two consecutive guide elementsin the flow direction of the water.

Hereinafter, the invention will be referred to in context ofconcentrating material located on or directly below a water surface.Such material may comprise, but is not restricted to, pollutionconsisting of oil floating on a water surface, chemicals, a solid in aparticulate form and loose objects. A solid in a particulate form may bedust, or it may be an absorbent containing, per se, pollution. Looseobjects may be waste, such as small and large bits of plastic, objectssuch as e.g. cans, jugs and ropes, or they may be natural objects suchas e.g. driftwood. The invention may also be used for concentrating liveor dead biological material, e.g. seaweed, kelp, algae and crustaceans,for example hill and Calanus finmarchicus, when being present naturally,or when being introduced so as to be present on or directly below thewater surface.

Oil pollution on a water surface is distinguished by a relatively smallamount of oil forming a large and relatively thin oil slick. Thisrenders collection of the pollution difficult, insofar as the collectionmust be carried out over a large area. The oil slick pollution may bebroken into smaller oil slicks, which renders the collection even moredifficult.

It is know within the art to use booms in order to restrict the adverseeffect of oil pollution on a water surface and in order to collect thepollution. Booms are distinguished by being provided with a buoyancybody and a skirt. The buoyancy body forms a barrier across the water,and the skirt, which is weighed down by a suitable weight, forms abarrier beneath the water. In order to be able to follow the motions ofthe waves, the buoyancy body and the skirt may be comprised of elasticmaterial, for example a plastic material. Further, the buoyancy body maybe inflatable. The advantage thereof is that the boom assumes littlespace, relatively speaking, during storage, transport and deployment,whilst assuming its full volume during use.

Booms may be used in several ways. One object may be to prevent a beacharea from becoming soiled by oil pollution. The boom then forms abarrier between e.g. the oil slick and the beach area. Another objectmay be to prevent dispersion by disposing the boom around an oil slick,after which the oil slick is collected by means of suitable equipment. Aboom may also be towed through an oil slick in order for the oil tobecome concentrated in a portion of the boom, thus making it easier tocollect the oil with, for example, so-called skimmers or pumps. For suchtowing, one and preferably two vessels may be used to tow the boombehind the free end portion thereof. Patent publication WO 02/12636describes the manner in which a boom may concentrate an oil spill anddiscloses a solution to how it may be collected. Patent publication WO2004/035937 discloses the manner in which a boom may be towed by twovessels through an oil spill area.

It is known in the art for booms, especially in the collection portionthereof, to be provided with an impervious bottom. Booms of this typeare referred to as an oil trawl. Further, it is known for a net to beused instead of an impervious bottom. Booms of this type are referred toas V-booms or net booms.

There are several disadvantages associated with the known types ofbooms, and the degree of effectiveness varies relative to the purposethereof. They are restricted in terms of the size of wave height theycan operate within before the oil is carried past the boom. Duringstowing oil and water up against the boom, the boom will belch, i.e. oilis forced down into the water near the boom and then is carriedunderneath the skirt and past the boom. Towing of the boom is carriedout at low speed, and generally two towing vessels must coordinate theirmovements in order for the boom to maintain its shape which, when seenfrom above, assumes a horseshoe-shape or a U-shape.

Upon towing the known booms, which mainly form a U-shape, the sides ofthe boom are referred to as arms, and the area between the free endportions of the arms are referred to as the front opening of the boom.Among other things, the collection efficiency of the boom, and the sizeof the area across which the boom can collect, depends on the width ofthe front opening and the tow speed of the vessel or vessels. It is alsoknown for the portions of the boom comprising the arms of the boom,which are substantially parallel, to contribute insignificantly to thecollection of the oil.

Besides the wave height, it is also known for the tow speed to belimited by the deep-draught of the skirt. At the longitudinal portion,which comprises the bottom portion or collection portion of a U-shaped,towed boom, a significant water resistance will be present, and thewater resistance increases with the deep-draught of the skirt. Thiswater resistance will also produce a stowing pressure in front of thefront opening of the boom. Given that the water with the pollution willdeflect and pass on the outside of the boom, the stowing pressure has ablocking effect on pollution which, desirably, is to enter into theboom. In order to counteract this effect, it is known to have, withinthe collection portion of the boom, an opening through which water andpollution may discharge from the boom. It is also known to be preferableto place collection equipment in this opening in the collection portionowing to the fact that the pollution will be most concentrated in thisportion. Upon using too high a tow speed, water and pollution will beforced down along the bottom portion of the boom's skirt and cause theboom to belch.

Thus, there is a need for a device that is capable of covering arelatively large area, and which can concentrate the pollution in amanner allowing the pollution to be collected using technology known perse. Further, there is a need for a device that is capable of beingoperated in the open sea using, preferably, one vessel, and which can betowed at a relatively high speed.

BRIEF SUMMARY OF THE INVENTION

The object of the invention is to remedy or to reduce at least one ofthe disadvantages of the prior art, or at least to provide a usefulalternative to the prior art.

The object is achieved by virtue of features disclosed in the followingdescription and in the subsequent claims.

In a first aspect, the invention concerns a device for concentration ofmaterial on or directly below a water surface, wherein the device isprovided with a front opening, with buoyancy bodies and with guideelements structured for guiding the material towards a collectionportion, and wherein the device is structured for admitting waterthrough the device in the flow direction of the water by virtue of thedevice, in a portion thereof, being provided with at least twoconsecutive guide elements in the flow direction of the water.

The guide element may be fixed to a form element. The form element maybe comprised of a net. In one embodiment, the form element may be of atriangular shape. In an alternative embodiment, the form element may becomprised of lines fixed to the guide elements so as to allow thedevice, when in its position of use, to assume a triangular shape, asviewed from above.

The guide element may be comprised of a buoyancy body, a skirt and aweight rope. A longitudinal direction of the guide element may form anangle of between 0° and 90° with respect to a width direction of thefront opening. This implies that the front opening forms an imaginarybase line, wherein the angle between the imaginary base line and thelongitudinal direction of the guide element is measured as an internalangle in a triangle where the guide element forms a side in thetriangle.

At least two guide elements may be substantially parallel. In analternative embodiment, the perpendicular distance between twoneighbouring guide elements may be smaller at the collection end of theguide elements than at the front end of the guide elements. Using thesame number of guide elements and the same front opening, the device ofthis embodiment will have a shorter distance between the front openingof the device and the end portion of the device, as compared to theembodiment where the guide elements are substantially parallel. In afurther alternative embodiment, the perpendicular distance between twoneighbouring guide elements may be larger at the collection end of theguide elements than at the front end of the guide elements. Using thesame number of guide elements and the same front opening, the device ofthis embodiment will have a larger distance between the front opening ofthe device and the end portion of the device, as compared to theembodiment where the guide elements are substantially parallel.

The collection portion of the device may be comprised of a mid-portion.Collected material, which is guided along the guide element until thematerial passes the collection end of the guide element, undergoesenhanced concentration from two sides in the mid-portion of the device.The collection portion of the device forms a channel in the device,wherein the channel extends from the front opening of the device ontothe end portion of the device. Two and two collection ends of the guideelements may form an opening in the mid-portion of the device. When twoand two guide elements are arranged symmetrically about the mid-portionof the device, as viewed from above, the distance between the collectionends of the guide elements will correspond to the width of thecollection portion.

The front opening of the device may be provided with spacers structuredfor towing behind a vessel. The spacer may be comprised of a door. Thisdoor may be a trawl door, a seismic deflector or some other form of doorknown in the art. This has the advantage of allowing the device to beoperated by one vessel.

In a second aspect, the invention concerns a method of concentratingmaterial located on or directly below a water surface by guiding thematerial through a device as described hereinbefore. The device may betowed on a water surface by means of at least one vessel.

In an alternative method, a front line of the device is fixed to thebanks of a river so as to allow river water to flow through and past thedevice.

BRIEF DESCRIPTION OF THE DRAWINGS

Hereinafter, an example of a preferred embodiment is described and isdepicted on the accompanying drawings, where:

FIG. 1 schematically shows the invention, as viewed from above, whereinsome of the elements are shown at different scales;

FIG. 2 shows the invention depicted in FIG. 1, wherein the device isfurther provided with a collection device;

FIG. 3A-C shows a cut-through section of a guide element and theposition of the guide element at different water flow velocities throughthe device; and

FIG. 4 shows the invention depicted when used to collect material in ariver course.

DETAILED DESCRIPTION OF THE INVENTION

In the drawings, reference numeral 1 denotes a device according to theinvention. The device is provided with several guide elements 12 andouter guide elements 18, 18′ fixed to a form element 3. In the figures,the form element 3 is depicted as a net.

A front line 32, at the end portions 34, 34′ thereof, is fixed to a door94, 94′. The doors 94, 94′ are connected to a vessel 9 with tow lines92, 92′. The vessel 9 moves along a water surface 8 and in a directiondenoted by a solid arrow. Upon movement of the vessel 9, the doors 94,94′, which are of a type known per se, will move out to the side of thevessel 9 when being pulled by the tow lines 92, 92′. The tow lines 92,92′ are comprised of a type known per se and may be comprised of ropesor metal wire. The doors 94, 94′ will stretch out the front line 32between themselves, whereby the front line 32 will assume a curvedshape, as viewed from above and depicted in FIGS. 1 and 2. Duringtowing, the end portions 34, 34′ of the front line will define a frontopening 2 of the device 1. By virtue of the vessel 9 towing the device 1in the direction marked with a solid arrow, the water in the watersurface 8 and a material 4 located on or directly below the watersurface 8, will move in a direction relative to the device, as denotedwith an open arrow in the figures.

The guide elements 12, 18, 18′ are fixed to the net 3 in such a way thatthe longitudinal direction of the guide elements 12, 18, 18′ is obliquerelative to the pulling direction of the device 1. The guide elements12, 18, 18′, at the front ends 120 thereof, are fixed to the net 3substantially at the front line 32. Collection ends 121 of the guideelements 12 end freely in a collection portion 14. The collectionportion 14 extends from the front line 32 onto an end portion 16. Thecollection ends 121 of the outer guide elements 18, 18′ may meet in theend portion 16 of the device 1. In an alternative embodiment, thecollection ends 121 of the outer guide elements 18, 18′ may beterminated somewhat apart from each other, whereby an opening 5 isformed between the collection ends 121, as shown in FIG. 2. In thisopening, the device 1 may be provided with a collection unit 52 of atype known per se, for example a so-called skimmer or an oil trawl. Thecollection unit 52 may be provided with a fluid connection 54 of a typeknown per se, which is structured to bring collected material 4 to acollection craft, for example the vessel 9.

Material 4 located on or directly below the water surface 8, and betweenthe doors 94, 94′ in the front opening 2, will encounter one of theguide elements 12, 18, 18′. Due to the relative movement between thedevice 1 and the water, the material 4, or parts of the material 4, willbe guided along the guide elements 12, 18, 18′ in the direction of thecollection portion 14. Some of the material 4 will move underneath theguide elements 12, 18, 18′. The material 4 moving underneath the outerguide elements 18, 18′ will then be inaccessible for furtherconcentration but may be further concentrated by repeating the sweepacross the area using the device 1. The material 4 moving underneath oneof the guide elements 12 will float up to the water surface 8 and thenencounter the following guide element 12 and thereafter be guidedtowards the collection portion 14. From FIGS. 1 and 2, the skilledperson will appreciate that this may be repeated several times. Thematerial 4 will be further concentrated in the collection portion 14,which forms a channel between the front line 32 and the end portion 16of the device. The material 4 being guided to the end portion 16 of thedevice will be significantly more concentrated than at the front opening2 and suitable for collecting with equipment known per se, for examplepumps or skimmers.

As shown in FIGS. 1 and 2, the device 1 is provided with several guideelements 12, which mainly have parallel longitudinal axes. The number ofguide elements is determined by the desired perpendicular distancebetween the guide elements 12, by the width of the front opening 2, andby the angle α which is formed between the guide elements 12 and thefront opening 2. In FIGS. 1 and 2, this angle is ca. 75°. This angle maybe an angle in the region from of 70°, inclusive, to 80°, inclusive, butnot limited to this angular region. It is up to the skilled person todetermine which angle is optimum, insofar as the optimum angle maydepend on which type of material 4 is desirable to concentrate further,for example oil or drifting seaweed. The optimum angle may also dependon the assumed wave height and assumed towing speed. As depicted inFIGS. 1 and 2, the angle is given as an internal angle measured from abase line extending between the doors 94, 94′. An angle of 0° willtherefore correspond to a direction being parallel to the base line.

As shown in FIGS. 3A-C, the guide element 12 is comprised of a lengthybuoyancy body 122 of a type known per se, and which is provided with askirt 124. The skirt 124 is cloth-shaped and surrounds a portion of thebuoyancy body 122. The skirt is provided with a lengthy weight in theform of a weight rope 126 of a type known per se. The weight rope 126may be fixed to the skirt 124 at the outside of the skirt 124. In analternative embodiment, the skirt 124 may surround a portion of theweight rope 126. The skirt 124 is fixed to the net 3 with a lashing 128,as shown in FIGS. 3A-C. Alternatively, the skirt 124 may be fixed to thenet 3 with a seam. In its position of use, when the device 1 is at restrelative to the water, the skirt 124 will be suspended down into thewater from the buoyancy body 122 so as to allow the weight rope 126 tobe located substantially below the buoyancy body 122, as shown in FIG.3A. The net 3 will be submerged in the water and be kept floating by theguide elements 12. The distance from the net 3 to the water surface 8 isdetermined by the deep-draught of the skirt 124.

The FIGS. 3A-C show the mutual positions of the buoyancy body 122, theskirt 124 and the weight rope 126 at increasing towing speeds for thedevice 1. The movement of the water relative to the device 1 is shownwith an open arrow. At a towing speed between 0 and 2 knots, as shown inFIG. 3A, the weight rope 126 will be located substantially below thebuoyancy body 122. At a towing speed between 2 and 4 knots, as shown inFIG. 3B, the weight rope 126 will be located substantially sidelong thebuoyancy body 122 and in a direction against the water flow. The net 3will be lifted closer to the water surface 8. At a towing speed between4 and 6 knots, as shown in FIG. 3C, the weight rope 126 will be locatedcompletely sidelong the buoyancy body 122 and in vicinity of the watersurface 8 in a direction against the water flow. The net 3 will belifted close to the water surface 8. The advantage thereof is that thetowing resistance of the device 1 is reduced at higher towing speedsowing to the fact that the deep-draught of the skirt 124 is reduced.Insofar as the material 4 is allowed to pass beneath one or severalguide elements 12 prior to being concentrated in the collection portion14, the deep-draught of the skirt 124 may be reduced without expendingtoo much of the collective capacity of the device 1 to concentrate thematerial 4 located on or directly below the water surface 8.

With respect other known solutions, the device 1 has a larger capacityfor concentrating material 4 located on or directly below the watersurface 8. For this purpose, it is advantageous that the front openingof the device 1 can be made very wide. It is known from gathering ofseismic data to use doors 94, 94′ forming a front opening from 1000 to1400 meters. In principle, the front opening 2 of the device 1 may bemade equally wide. The capacity also depends on the speed of the towing.Thus, it is advantageous that the deep-draught of the skirt 124decreases at increasing towing speeds. Given that the structure of thedevice 1 is flexible and simultaneously is kept in position by theextended form element 3, the device 1 may also be used for larger waveheights than when using traditional booms.

The skilled person will appreciate that the device 1 may be stored andtransported on board a vessel 9 in the same manner as that of the trawlsand trawl bags used for fishing. Alternatively, the device 1 may bestored and transported on board a vessel 9 in the same manner as forequipment intended for carrying out seismic surveys offshore. Deploymentand retrieval of the device 1 may therefore be carried out in a mannerknown per se.

In an alternative embodiment, as shown in FIG. 4, the device 1 may becomprised of substantially half of the device shown in FIG. 1. Thisimplies that the net 3 is of a triangular shape with an associated guideelements 12 extending substantially in one longitudinal direction only.Then the collection portion 14 will comprise a side edge of the device1, and the device 1 includes only one outer guide element 18. Such anembodiment may prove advantageous in context of concentrating materialin a river 6. The front portion 2 may extend across a surface portion ofthe width of the river 6, possibly across the entire width of the river6. With its end portions 34, 34′, the front line 32 of the net is fixedat each river bank 62, 62′. The river water will flow past the device 1,and the device 1 will guide the material 4, which is located on ordirectly below the water surface, inward to the one river bank 62 wherethe material 4 may be collected in a manner known per se. This also hasthe advantage of the flow velocity being lower along the river bank 62than in the midst of a river 6, which makes it easier to collect thematerial 4 along the river bank 62.

In an alternative embodiment (not shown), the guide elements 12, 18, 18′are comprised of narrow-spaced buoyant balls of a type known per se. Inthis embodiment, the buoyant balls may be attached both to the lowerside and the upper side of the net 3, whereby the buoyant balls alsocomprise the skirt 124 of a guide element, and no weight rope 126 isused.

In a further alternative embodiment (not shown), the guide element 12 iscomprised of a thick buoyant rope fixed to the net 3. The skilled personwill also know that such a buoyant rope may comprise a part of the meshthread of the net 3.

The foregoing description details certain preferred embodiments of thepresent invention and describes the best mode contemplated. It will beappreciated, however, that changes may be made in the details ofconstruction and the configuration of components without departing fromthe spirit and scope of the disclosure. Therefore, the descriptionprovided herein is to be considered exemplary, rather than limiting, andthe true scope of the invention is that defined by the following claimsand the full range of equivalency to which each element thereof isentitled.

1. A device for concentration of material on a water surface, saiddevice comprising: a front opening; buoyancy bodies; guide elementsstructured for guiding the material towards a collection portion; thedevice being structured for admitting water through the device in a flowdirection of the water; and at least two consecutive guide elements inthe flow direction of the water being provided in a portion of thedevice.
 2. The device according to claim 1, wherein said guide elementsare fixed to a form element.
 3. The device according to claim 2, whereinsaid form element includes a net.
 4. The device according to claim 2,wherein said form element is of a triangular shape.
 5. The deviceaccording to claim 1, wherein said guide elements further include abuoyancy body, a skirt and a weight rope.
 6. The device according toclaim 1, wherein a longitudinal direction of said guide elements form anangle of between 0° and 90° with respect to a width direction of saidfront opening.
 7. The device according to claim 1, wherein at least twoguide elements are substantially parallel.
 8. The device according toclaim 1, wherein said collection portion of said device includes amid-portion of the device.
 9. The device according to claim 1, whereintwo and two collection ends of said guide elements form an opening in amid-portion of said device.
 10. The device according to claim 1, whereinsaid device is provided with spacers structured for towing behind avessel.
 11. The device according to claim 10, wherein said spacersincludes a door.
 12. A method of concentrating material located on ordirectly below a water surface, said method including the followingstep: guiding concentrated material through a device having a frontopening, buoyancy bodies and guide elements structured for guiding thematerial towards a collection point of the device, at least twoconsecutive guide elements being provided in the flow direction of thewater, and the water being admitted through the device.
 13. The methodaccording to claim 12, including the step of towing the device on thewater surface by means of at least one vessel.
 14. The method accordingto claim 12, including the step of fixing a front line of the device tobanks of a river, whereby river water flows through and past the device.